Refrigeration system



May 10, 1938. P. F. sHlvERs 2,116,801

` REFRIGERATION SYSTEM i Filed June 27, 1934 IHHHHHHH mm fl [nue/nger Paul jf? Jzz/enf Bg 2221s QFor/769.5

Receiver' :ummm

Patented May 10, 1938 nEmIGEnA'rIoN SYSTEM I Paul F. Shivers, Wabash, Ind., assigner to Minneapolis-Honeywell Regulator Company, Minneapolis, Minn., a corporation of Delaware Application June 27, 1934, Serial No. 732,637

Y31 Claims.

The present invention relates to improvements inautomatic refrigerating systems.

Refrigerating systems can be classified into two groups, one of which is commonly termed dry expansion systems and the other of which is generally termed ooded systems.` In a dry expansion system, the expansion or cooling coils are only partially filled with liquid refrigerant, the remainder of the coils being filled with refrigerant in a gaseous state. In flooded systems, the expansion or cooling coil is maintained full of liquid refrigerant. In order to provide a flooded system, it has been common practice to provide a header or surge drum to which vis connected a plurality of cooling or expansion coils, both ends of such coils being connected to the surge drum. The surge drum is partially lled with liquid, and all of the cooling coils are completely filled with liquid. As the liquid absorbs heat and is changed into a gas, the gas bubbles up through the liquid in the surge drum and returns to the suction side of the compressor. The surge drum is further provided with a oat which responds to the level of the liquid in the surge drum and controls the flow of liquid to the surgedrum from the condenser or liquid receiver through a suitable valve.

These flooded systems are known to be very eflicient but have the disadvantage of requiring the complicated mechanism above described. In other words, it has heretofore only been possible to provide aiiooded systemQoy providing a complicated unit including the\expansion or cooling coils, the surge drum and the float valve mechanism, it being impossible by the apparatus heretofore known to change over a dry expansion system to a flooded system or to operate a simple yexpansion or cooling coil on the flooded principle Without making the expansion coil a part of a ti0 complicated unitary structure.

' Furthermore, in order to operate a plurality of cooling or expansion coils operating on either the dry expansion or flooded principle from a single Vcompressor wherein it is desired to' maintain two or more of the expansion or cooling coils at different temperatures, it has been necessary to provide additional mechanism in the form of a Y 55 the provision of a fiooded or substantially flooded (ci. cs2-sr refrigeration system which does not require a oat mechanism of any type and which can be applied to existing expansion or cooling coils operating upon the dry expansion principle, as well as being applicable to any simple expansion coil, 5 whereby the operating advantages of a flooded system may be obtained substantially while eliminating the mechanical and constructional complications and limitations thereof.

A further object of theinvention is the provision of a unitary valve mechanism, which does not include any float'structures whatsoever, that is adapted to be applied toany ysimple expansion coil so as to operate the same on a flooded principleand maintain the proper coil temperature without any additional mechanism, even though the coil be one of a group of coils operated from a single compressor and at` different coil temperatures.

Another object of the invention is the provision of a valve that is controlled by the conjoint action of the back pressure and the temperature of the refrigerant on the suction side of the expansion coil in such manner that the valve is not only normally operated by the thermostat or not the coil be flooded, when the back pressure falls to a predetermined value indicating that the desired `average coil temperature has been established.

A further object of the invention is the provision of a refrigeration valve mechanism including `a suction line valve that is controlled conjointly by the suction pressure and by a single thermostat responsive to the temperature of the refrigerant in the suction line, this single thermostat also operating an expansion valve on the inlet side of the expansion coil.

Another4 object of the invention is the pro-- vision of a thermostatic expansion valve in which the expansion valve is not only controlled by a thermostat,but which is automatically conditioned for such control only at such times that the high side pressure is sufficient to provide proper operation 'of the cooling coil.

, Other objects of the invention .will be found in the drawing, the detailed description, and the appended claims.

For a more complete understanding of the invention, reference may be had to the following description and the accompanying drawing, in which: 'q

Fig. l is a diagrammatic showing of a refrigerating system with my improved valve mechas its other end abuts a spring retainer 36 which' `lanism applied thereto, the valve mechanism being shown in section and upon an enlarged scale,

and

Fig. 2 is a reduced size section of the valve mechanism taken about on line 2-2 of Fig. 1.

Fig. 3 is a fragmentary sectional View taken on line 3-3 of Figure 1.

Referring to the drawing, the system of the present invention includes a valve mechanismn generally indicated at I which includes an upper casting II and a lower casting I2 which are secured together by suitable means, such as the screws I3. Interposed between the upper casting Il and the lower casting I2 is a sealing member It and a pair of suitable gaskets I5. The upper and lower castings II and l2, together with other mechanism to be hereinafter described, form a high pressure inlet chamber I6, a control chamber I1, a low pressure inlet chamber I8, anda low-pressure outletchamber I9.

The lower casting I2 is provided with a boss 2l] having an internally screw-threaded bore 2l which receives an outlet valve plug 22., there being suitable packing 23 interposed therebetween. The valve plug 22 is provided with a valve opening 2d with which a vneedle valve 25 cooperates. The valve plug 22 is provided with an extension 26 which serves to guide the needle valve 25.`

The needle valve 25 is provided with a valve stem 21, of Vreduced diameter, the extended end of which is formed with an enlarged head 28 which is adapted to abut, under certain conditions, the bellows head 29 of a bellows 39. The open end of the bellows 30 is secured to an annulus 3I which is sealed to shoulders 32, formed by an opening in the upper casting II, as by means of soldering. A plate 33, which is secured by screws 34, closes off the interior of bellows 30. The bellows 30 is normally expanded by means of a relatively heavy coiled expansion spring 35 so that valve 25 normally closes the valve opening 24. One end of spring 35 abuts bellows head 29 whereis positioned by a screw 31.

An actuator comprises a pair of levers 38 and 39, which are held in spaced relation by means of spacers 4|) and 4I and are pivoted upon a pin 42 that is journalled in the lower casting I2. The pin 42 is held in place by an enlarged screwthreaded portion 43 thereof which is received by l suitable screw threads formed in a boss 44 of the lower casting I2. The extended ends of the members 38 and 39 straddle the guide extension A combined collar and spring retainer 45v 28 of valve stem 21 and thecoiled spring 41, and

has one of its ends abutting the collar 45, whereas its other end abuts the bellows head 29.

When the levers 38 and 39 are in a substantially horizontal position and when the bellows. head 29 is subjected to a low or atmospheric pressure, the stronger spring 35 partially compresses the spring 48 and holds valve 25 in its closed position. If the left-hand ends of levers A38 `and 39 are moved downwardly, the collar 45 is lifted and the spring 48 is compressed, the bellows head 29 remaining stationary so that valve 25 re- -mains in its closed position. Now, if the bellows head 29 is subjected to a predetermined pressure,

it moves upwardly compressing spring 35, whereupon springs 41 `and 48 expand, the spring 41 in expanding lifting the valve 25 and moving the same to open position. The expansion of spring 48 continues as long as bellows head 29 continues to move upwardly; but expansion of spring 41 and lifting of valve 25 is limited by engagement of the valve 25 with the collar 45. If the left-hand ends of'levers 38 and 39 are now moved upwardly so as to lower the righthand ends thereof, the collar 45 moves the valve 25 downwardly under the action of spring'48 to an extent determined by the downward movement of the right-hand ends of levers 38 and 39, or until valve 25 completely closes the valve opening 24. In this manner, when the bellows head 29 is raised by being subjected to the proper pressure, the valve 25 is positioned in accordance with the movements of the levers` 38 and 39. Whenever the pressure acting upon the bellows head 29 is released, the strong spring 35 moves the bellows head downwardly against spring 48, and against spring 41 if the valve 25 is raised, so as to close the valve. In other words, the arrangement thus far described 'provides a valve, th action of which is dominated by a pressure responsive member in the form of the bellows head 29 so that the valve is held closed whenever the pressure responsive member is subjected to less than a predetermined pressure, but when the pressure responsive member is subjected to a larger pressure, the valve may be opened or closed in accordance with the movements of the levers 38 and 39. The movements of levers 38 and 39 are controlled by mechanism now to be described.

A pair of bellows 50 and 5I have their open ends sealed to the' sealing member I4. The upper bellows 50 extends into the low pressure outlet `chamber I9 and is provided with a head 52. The lower bellows I extends into the control chamber I1 and is provided with a heayd 53, the arrangement being such that the bellows 50 and 5Iv formlan enclosed expansible chamber 54. The

head 53 is provided with a boss.55 and the head through which a suitable charge of volatile fluidv may be admitted to the chamber 54, after which the opening 59 is sealed off as by a set screw 60. The bellows 50 and 5I and the spring 58, together with the charge of volatile fluid in the chamber 54 formed thereby, therefore comprise a thermostatic element. r

The lower end of lower casting I2 is open and receives a bellows 65, the open end of which is sealed to an annulus 66 that is in turn/ sealed to the lower casting I2. A cap 61 closes oil` the interior of bellows 65. The bellows 65 is provided `with a bellows head 68 which has a screw threaded extension 69 that is adapted to be threaded into the bellows head 53 of bellows 5I. The levers 38 and 39 extend throughfan opening 10 lformed in the lower casting I2 and straddlethe exten- -sion 69, so that they are disposed between the bellows head sa and its other end abutting a.

spring retainer 12 which may be adjustably positioned by means of a screw 13 that passes through the cap 61 in screw-threaded relation therewith.

The upper casting is provided with a partition wall 15 which separates the low pressure inlet and outlet `chambers I8 and I9, this partition wall 15 being provided with a valve opening 16. A cooperating valve disc 11 is threaded upon an extended portion of bellows head 56, and under certain conditions abuts the bellows head 18 of a bellows 19. The bellows 19 has its open end sealed to an annulus 80 which is suitably sealed to the upper casting A cap 8| closes off the interior of bellows 19. A coiled spring 82 has one of its ends abutting the inner face of bellows head 18 and its other end abuts a spring retainer 83, the position of which may be adjusted by a screw 04 which is threaded into the cap 8|.

This valve mechanism l0 is adapted to be` utilized in conjunction with a refrigeration systern which includes a compressor 90 that is operated by a compressor motor 9|. `'I'he compressor 90 is adapted to compress the hot gaseous refrigerant in the usual known manner, after which is it transmitted to a condenser 92 by means of a pipe 93. 'Ihe condenser 92` is provided with a suitable cooling coil indicated at 94. The condenser 92 serves to condense the compressed gaseous refrigerant and transforms it into a liquid, after which it passes to a liquid receiver 95 by means of a pipe 96. 'Ihe liquid from liquid receiver 95 is transmitted by a pipe 91 to the high pressure chamber I6, the pipe 91 being connected to a suitable boss 98 formed in the lower casting I2. The outlet valve plug 22 is connected to an expanslonor cooling coil 99 by means of a pipe |00. The other end of the l expansion coil 99 communicates with the lowpressure inlet chamber I8 by means of a pipe I 0| which is connected to a suitable `poss |02 formed in the upper casting I I. The low pressure outlet chamber vI9 communicates with the compressor 90 by means 'of a pipe |03 which is connected to a boss |04 formed in the upper casting The compressor motor 9| is adapted to be controlled by a pressure switch, generally indicated at |05, which includes a mercury switch |08 that closes when the return pressure in line |03 reaches a predetermined high value and opens when the pressure therein is reduced to a predetermined minimum, the setting of this switch |06 depending upon the average temperature it is desired to maintain in coil 99 or in the coldest coil if a plurality of coils are used. The circuit for compressor motor 9| includes line wire |01, mercury switch |06, a wire |08, motor 9|, and line wire |09.

Operation With the parts in the position shown, thesupply of electrical power to the compressor motor 9| is disconnected so that the system is completely shut down and not operating automatically. As a result, there is no pressure on the high side of the system, andthe spring is therefore able to extend the bellows 30 so that the valve 25 is closed as hereinbefore described. The low side temperature is also high so that thebiasing elect of the expansion of the volatile uid in chamber 54 and the expansive force of 93. The condenser 92 liquees the gaseous refrigerant, after which it passes to receiver 95 by.

pipe 90, the hot liquid thereafter passing to the high pressure inlet chamber I8 by way of pipe 91. As this high side pressure increases, the bellows head 29 is moved upwardly against the action of spring 35. The spring 41 causes the head 28 'of valve stem 21 to follow the bellows head 29 thereby opening the valve 25. The valve 25 continues to'open as the bellows head 29 continues to move upwardly under the increase in pressure on the high side until such time as the valve 25 engages the collar 45. The liquid refrigerant also passes through opening 10 and into control chamber I1. It exerts equal forces against bellows head 53 and 68, which are of equalsize, so that the positions of levers 38 and 39 are not affected by the pressure of the liquid refrigerant. Liquid refrigerant now passes to the cooling coil 99 by way of pipe |00 wherein it evaporates in lowering the temperature of the compartment being controlled. The evaporated liquid passes into low pressure inlet chamber I8 and through the valve opening I9 to the low pressure outlet chamber I9, from which it returns to the compressor b`y pipe |03. During the starting of the system, the gas returning from. the cooling coil 99 will be at a relatively high temperature and pressure, so that the valve disc 11 will remain in open position.' The continued feeding of liquid to the cooling coil 99 will soon iill this coil and cause the liquid to pass through the low pressure inlet chamber I8 and into the low pressure outlet chamber I9, whereupon the volatile fluid in the upper portion of chamber 54 will be cooled and the pressure in chamber 54 reduced. This reduction in pressure is supplemented by the action of spring 82 to overcome the expansive force of spring 58, whereupon valve disc `11 is moved toward closed position by the contraction of bellows 50. Likewise. contraction of bellows 5I under the action of spring 1| moves the right hand ends of levers 38 and 39 downwardly to permit spring 48 to lower collar and partially close valve 25. In this manner, the thermostat comprised by the bellows and 5| and the charge of volatile iluidtherein contained controls the valve disc 11 and the valve 25 to establish such a flow of refrigerant through cooling coil 99 as to maintain the temperature of the thermostat at the proper and desired point whereby the expansion or cooling coil 99 is normally maintained ooded.

As the temperature of the compartment to be controlled is lowered, the back pressure on the cooling coil 99 and in the low pressure inlet chamber I8 is reduced. If this back pressure should reach a predetermined low point indicata,Y

ing that the temperature of the compartment being controlled has been lowered to the desired point, this lowering in pressure operating against bellows head 18 permits spring 82 to exert a greater force against the valve disc 11, Awhereupon the valve disc 11 will be moved toward closed position and will close when the back pressure decreases to a value indicating that the compartment being controlled is at the desired temperature irrespective of the temperature of the thermostat comprised by bellows 50 and 5|. Whenever the pressure in suction line |03 becomes lower than the ipredetermined minimum, the switch |06 will open to deenergize compressor motor 9| until the pressure in suction line |03 rises to the desired maximum.

In this manner, the bellows 19 and its associated spring 02 operate to close valve disc 11 at a predetermined back pressure indicating that the compartment temperature has been lowered to the proper value. As long, however, as the back pressure is higher than that back pressurev which indicates the compartment temperature is at the desired value, the thermostat operates to position the outlet valve disc 11 and the inlet valve 25 to maintain the coil 99 full of liquid refrigerant.

While I have shown a suction pressure controller for controlling the operation of the compressor, it will be understood that I do not limit myself to this, and if desired, a thermostat responsive to the temperature of the compartment cooled by the coil 99 may be employed in place of said suction pressure controller.`

The system of the present invention therefore operates through its thermostat to maintain the cooling coil 99 flooded at all times during which the compartment temperature is higher than that desired and, by means of the back pressure responsive mechanism defined by bellows 19 and spring 02, operates to close off the suction line by moving valve disc 11 to closed position whenever the back pressure falls vto a value indicating that the compartment or cooling coil has been lowered to the proper temperature. In this manner, the system of the present invention operates asa ooded system without the use of the usual expensive float and boiler construction which characterize the ordinary flooded system. The system of the present invention further operates to prevent the back pressure from decreasing below a predetermined point, so that the proper compartment temperature is maintained. Further, this arrangement allows the connecting of a n umber of cooling coils to a single compressor and maintains the proper back pressure and flooded 'condition in each of the cooling coils without utilizing the usual electromagnetic suction valve for each cooling coil and the cooperating thermostat located in the associated compartment.

While a specific embodiment of the invention has been herein described, it will readily be seen that many changes can be made without departing from the spirit of the invention, and I therefore intend to be limited only by the following claims. It will be particularly evident that if it is desired to have the thermostat control the expansion or inlet valve 25 without relation to the inlet refrigerant pressure, the levers 38 and 39 can be connected directly to the valve 25, the

bellows 30 and springs 35, 41, and 48, and associated parts being eliminated.

I claim: l

1. The combination with an expansion coil having its high pressure side connected to a suitable supply of liquid refrigerant and its low p ressure side connected to a compressor, of a valve for interrupting communication between the expansion coil and compressor, means responsive to the temperature of the refrigerant on the low pressure side of the'expansion coil for operating the valve to maintain said temperature substantially constant, and a device responsive to the pressure ofthe refrigerant on the low pressure side of the expansion coil for closing the valve, irrespective of the refrigerant tempera-ture, when said pressure falls to a predetermined minimum.

2. The combination with an expansion coil having its high pressure side connected to a suitable supply of liquid refrigerant and its low pressure side connected to a compressor, means for reducing the vapor pressure of the refrigerant in said coil, a valve for interrupting communication between the expansion coil and compressor, means responsive to the temperature of the refrigerant on the low pressure side of the expansion coil for operating the valve to maintain the expansion coil normally filled with liquid refrigerant, a device responsive to the pressure of the refrigerant on the low pressure side of the expansion coil for closing said valve at a predeteran outlet chamber and a partition wall therebetween having a valve opening therein, and a valve for closing the valve opening, a thermostat located in the outlet chamber for controlling the valve. a pressure responsive member located in the inlet chamber and moved in valve opening direction by the pressure in the inlet chamber, and means biasing the pressure member to valve closed position for closing the valve when the pressure in the inlet chamber falls to a predetermined minimum. A v

4. The combination with an expansion coil, of an inlet valve for controlling the supply of liquid refrigerant flowing directly to the expansion coil, an 4outlet valve for controlling the flow of refrigerant from the expansion coil, and means directly responsive to the temperature of the refrigerant leaving the expansion coil for closing both valves as the leaving refrigerant temperature falls to a predetermined minimum.

5. The combination with an expansion coil, of an inlet valve for controlling the supply of liquid refrigerant to the expansion coil, an outlet valve forcontrolling the flow of refrigerant from the expansion coil, and a single thermostat directly responsive to the temperature of the refrigerant leaving the expansion coil for operating both valves to .close the same when the temperature at said thermostat decreases to a value indicating that the expansion coil is substantially lled with liquid refrigerant.

6. The combination with an expansion coil, of

supply of liquid refrigerant, of a unitary valve mechanism, comprising, an 4 outlet valve for controlling the flow of refrigerant from the expansion coil to the compressor, an inlet valve for controlling the flow of liquidrefrigerant to the expansion coil, thermostatic means responsive to .the temperature of the refrigerant leaving the expansion coil for closing both valves when the temperature of the leaving refrigerant falls to a A value indicating that the expansion coil is lled with liquid refrigerant, and means controlled by the pressure on the low side of the expansion coil for closing the outlet valve irrespective of the leaving refrigerant temperature when the low side pressure falls to a predetermined value.

8. The combination with an expansion coil having its low pressure side connected to a compressor and its high pressure side connected to a supply ofliquid refrigerant, 'of a unitary valve mechanism, comprising, an outlet valve for controlling the iiow of refrigerant from the expansion coil to the compressor, an inlet valve for the pressure of the liquid refrigerant for permitting the thermostatic means to open the inlet valve only in the event the refrigerant supply pressure is sufficiently high.

9. ,'Ifhe combination with an expansion coil having its 10W pressure side connected to a compressor and its high pressure side connected-to a supply of liquid refrigerant, of a unitary valve mechanism, comprising, an outlet valve fo'r controlling the flow of refrigerant from the expansion coil to the compressor, an inlet valve for controlling the W of liquid refrigerant to .the expansion coil, thermostatic means responsive to the temperature of the refrigerant leaving the expansion coil for closing both valves when the temperature of the leaving refrigerant falls to a value indicating that the expansion coil is lled with liquid refrigerant, means controlled by the pressure of the liquid refrigerant for permitting the thermostatic means .to open the inlet valve only in the event the refrigerant supply pressure is sufficiently high, and means responsive to the refrigerant pressureon the low pressure side of the expansion coil for closing the outlet valve when the low side pressurel falls to a predetermined minimum irrespective of the'temperature of the thermostatic means. n

10. The combination with an expansion coil having its inlet side connected to a. supply of tothe refrigerant supply pressure for permitting opening movement of the inlet valve by the thermostat only when the supply pressure is above a given minimum.

1l. The combination with an expansion coil having its inlet side connected to a supply of liquid refrigerant, of an inlet valve controlling the ow of refrigerant Ato the expansion coil, a thermostat responsive to the temperature of the refrigerant leaving the expansion coilV for opening the inlet valve when .the leaving refrigerant temperature is Aabove a given minimum, means responsive to the refrigerant supply pressure for permitting opening of the inlet valve by the thermostat only when'the supply pressure is above a given minimum, an outlet valve controlling .the flow of refrigerant from the expansion coil, and means responsive to the pressure of the refrigerant leaving the expansion coil for closing the outlet valve when said pressure falls to a given minimum.

12. A refrigeration valve structure of the class described, comprising, in combination, a casing including an inlet chamber and an outlet chamber with a partition wall therebetween having a valve opening therein, a valve disc for closing the valve opening, a thermostat located in the outlet chamber and connected to the valve for closing the samewhen the temperature in the outlet chamber falls to a given minimum, a pressure member located in the inlet chamber and adapted to engage the valve for closing the same, and a spring biasing said pressure member toward valve closed position whereby the spring closes the valve if the pressure in theinlet chamber falls to a given minimum.

13. A refrigeration valve structure of the class described, comprising, in combination, a casing `means defining high and low pressure inlet and outlet passages, a high pressure valve and a low pressure valve, and a thermostat located in the low pressure outlet passage for closing both the valves when the temperature in the low pressure outlet passage falls to a predetermined minimum.

14. A refrigeration valve structure of the class described, comprising, in combination, a casing defining high and low pressure inlet and outlet chambers, a high pressure valve and a low pressure valve, a thermostat located in the low pressure outlet chamber for closing both the valves when the temperature in the low pressure outlet chamber falls to a predetermined minimum, a pressure responsive member located in the low pressure inlet chamber and adapted to engage the low pressure valve for closing the same, and a spring biasing the pressure member to valve closing position whereby the low pressure valve is closed whenever the pressure in the low pressure inlet chamber falls to a given minimum irrespective of the temperature at the thermostat.

15. A refrigeration valve structure of the class described, comprisingin combination, a casing defining high and low pressure inlet and outlet chambers, a high pressure valve and a low pressure valve, a thermostat located in the low pressure outlet chamber for closing both the valves when the temperature in the low pressure outlet chamber falls to a predetermined minimum, a pressure responsive member responsive to the pressure in the high pressure inlet chamber, and a spring biasing the pressure member to valve closing position whereby the high pressure valve can only be opened by the thermostat if the pressure in theA high pressure inlet chamber is suinciently high.

16. A refrigeration Valve structure of the class described, comprising, in combination, a casing defining high and low pressure inlet and outlet chambers, a high pressure valve and a low pressure valve, a thermostat located in the low pressure outlet chamber for closing both the valves when the temperature in the low pressure outlet chamber falls to a predetermined minimum, a pressure responsive member responsive to the pressure in the high pressure inlet chamber, a spring biasing' the pressure member to valve closing position whereby the high pressure valve can only be opened by the thermostat if the pressure inthe high pressure inlet chamber is sufficiently high, a second pressure responsive member responsive to the pressure in the low pressure inlet chamber adapted to close the low pressure valve, and a spring biasing the second pressure member to valve closed position whereby the low pressure valve is closed whenever the pressure in the low pressure inlet chamber falls to a given minimum.

17. A refrigeration valve of the class described` comprising, in combination, a casing defining an inlet chamber and an outlet chamber with a partition wall therebetween having a valve opening therein, a valve for closing the valve opening, a pressure member located in the inlet chamber and moved in valve opening direction upon an increase in the inlet chamber pressure, a. spring biasing the pressure member in valve closing direction, .an extensible connection between the pressure member and valve for maintaining the valve closed irrespective of the position of the pressure member, and a thermostat capable of shortening said extensible connection to open the valve if the pressure member is moved to a predetermined position in valve opening direction.

18. The combination with `a cooling coil having its inlet side connected to a supply of liquid refrigerant, of an inlet valve controlling the 110W of refrigerant to the expansion coil, a thermostat for controlling said valve to open the same as the temperature to which the thermostat responds rises, and means responsive to the refrigerant supply pressure for permitting opening of said valve by the thermostat only when the supply pressure is above a given minimum.

. 19. The combination with an expansion coil adapted to have its suction end connected to a compressor and its inlet end connected to a suitable supply of liquid refrigerant, of a valve mechanism comprising a casing defining an inlet chamber adapted to be connected to the expansion coil, an outlet chamber and a partition wall therebetween having a valve opening therein, and a valve for closing the valve opening, a thermostat responsive to the temperature of the refrigerant passing through said valve fr controlling the same to close the valve as such temperature falls, a pressure responsive member located in the inlet chamber and moved in valve opening direc.

tion by the pressure in the inlet chamber, and means biasing the pressure member Yto valve closed position for closing the valve when the pressure in the inlet chamber falls to a predetermined minimum.

20. The combination with an expansion coil having its inlet side connected to a supply of liquid refrigerant, of an, inlet valve cohtrolling the flowkof refrigerant to the expansion coil, said valve being movable in only one direction to close the same and in the opposite direction to open the same, biasing means biasing said valve towards closed position, pressure responsive means-re-` sponsive to the pressure of the liquid refrigerant working in opposition to said biasing means whereby the valve is freed for opening and closing movements when the pressure of the liquid refrigerant is sufficiently high, and means automatically controlling said valve to open and close the same in response to demands when the valveA is thus freed for opening and closing movements.

21. A device of the character described, comprising in combination an expansion coil having its high pressure side connected to a suitable supply of liquid refrigerant and its low pressure yside connected to a compressor, a plurality of valves arranged for interrupting communication between said coil and said compressor in a manner to control the quantity' of liquid refrigerantin said coil, temperature responsive means arranged for operating said valves to maintain theexpansion coil normally filled Lwith liquid refrigerant, and independent pressure responsive means to close one of said valves responsive to a fall in.

pressure to a predetermined value, and prevent opening of said valve by said temperature responsive means until said pressure has risen.

22. A device of the character described, comprising, in combination, an expmsion coil having its high pressureside connectedy to a suitable supply of liquid refrigerant and itslow pressure side connected to a compressor, a plurality of valves arranged for interrupting communication between said coil andy said compressor in a manner to control the quantity of liquid refrigerant in said coil, and temperature responsive means arranged for operating said valves to maintain the expansion'coil normally filled with liquid refrigerant, said temperature responsive means comprising an expansion chamber containing a temperature responsive volatile fluid.

23. The combination with an expansion coil having its high pressure side connected to a sultable supply of liquid refrigerant and its low pressure side connected to a compressor, means for reducing the vapor pressure of the refrigerant in said coil, means for maintaining said coil substantially full of liquid refrigerant while preventing a ow of liquid refrigerant to said compressor, said means comprising a valve interposed in the path of iiow of the refrigerant leaving said evaporator, and a thermostat subjected to the temperatureof the outgoing refrigerant, said thermostat being arranged for closing said valve when the temperature of the outgoing refrigerant indicates an approach of liquid refrigerant to said valve and for opening said valve upon an increase in said temperature.

24. In a refrigeration system, an evaporator having an inlet and an outlet, a compressor connected to supply refrigerant to the inlet, and to withdraw refrigerant from the outlet, means for stopping and starting the compressor in accordance with the load on said evaporator, a valve'in the outlet, thermostatic means responsive to the temperatureof the outgoing refrigerant. in control of said valve, a valve in said inlet, and means responslbe to the head pressure of said compresvsor for closing said inlet valve when the compressor is out of operation.

25. In a refrigeration system, in combination, an evaporator, having an inlet and an outlet, means for supplying refrigerant to the inlet of said evaporator, back-pressure reducing neans connected to said outlet, an outlet control valve'interposed between the outlet and the back-pressure reducing means, means responsive to the temperature of the outgoing refrigerant for actuating said valve, a valve in said inlet, control means for placing said back pressure reducing means into and out of operation, and means controlled by said control means for closing said inlet valve substantially simultaneously with the placing of said back pressure reducing means out of operation.

.said evaporator, means for causing evaporation of refrigerant within said evaporator including back-pressure reducing means connected to said.

outlet, an outlet cont-rol valve interposed between the outletand the back-pressure reducing means, means responsive to the temperature of the outgoing refrigerant for actuating said valve, and automatic means responsive to a condition indicative of operation or non-operation of sai-d backpressure reducing means for 'preventing flow of refrigerant when said back-pressure reducing means is out of operation.

27. In a refrigeration system, in combination,

an evaporator having an inlet and an outlet, means for supplying liquid refrigerant to said evaporator inlet, back-pressure reducing means connected to said evaporator outlet for with.- drawing evaporated refrigerant therefrom, valve means for controlling the flow of liquid refrigerant lnto said evaporator, means responsive to the pressure of the liquid refrigerant for controlling said valve means, said pressure responsive means being arranged for causing movement of said valve means towards closed position upon a decrease in pressure of said liquid refrigerant, and means responsive to the pressure of the refrigerant in said evaporator for cooperating with said rst pressure responsive means in controlling said valve means, said second pressure responsive means being arranged to induce movement of said valve means towards open position upon a decrease in pressure in said evaporator.

28. An expansion valve for refrigeration sysl tems, comprising a valve casing formed to provide a valve chamber and a diaphragm chamber, Y

said chambers being in communication, means for supplying liquid refrigerant to said chambers,

, a valve means in said valve chamber for controlling the ow of liquid refrigerant fromsaid chamber, diaphragm means in said diaphragm chamber, said diaphragm means being subjected on one side to a pressure to be controlled and on its other side to said liquid refrigerant, means associated with said diaphragm means and said valvermeans for actuating said valve means by movements of said diaphragm means, and second diaphragm means in said diaphragm chamber, said second diaphragm means being associated with said first diaphragm means in a manner to prevent changes in pressure of said liquid refrigerant from influencing said first diaphragm means. n

29. An expansion valve for refrigeration systems, comprising a valve casing formed to provide a valve chamber and a diaphragm chamber, a partition wall between said valve chamber and said diaphragm chamber, an opening in said partition wall for providing restricted communication between said valve chamber and said diaphragm chamber, means for supplying liquid refrigerant to said valve chamber, valve means in said valve chamber for controlling the ow of liquid refrigerant from said chamber, a diaphragm in said diaphragm chamber, said diaphragm being subjected on one side to a pressure to be 'controlled and on its other side to said liquid refrigerant in a manner to cause movement of said diaphragm upon change in .said pressure to be controlled, and means extending from said diaphragm through the opening in said partition to said valve means for actuating said valve means by movements of said diaphragm.

30. An expansion valve for refrigeration systems, comprising a valve casing formed to provide a valve chamber and a diaphragm chamber, said chambers being in communication, means for supplying liquid refrigerant to said chambers,

lil

a valve means in said valve chamber for controlling the flow of liquid refrigerant from said chamber, a diaphragm` in said diaphragm chamber, said diaphragm being subjected on one side to a pressure to be controlled and on its other. side to said liquid refrigerant, means associated with said diaphragm and said valve means for actuating said valvel means by movements of said diaphragm, seal-off diaphragm means in said diaphragm-chamber, said seal-off diaphragm means having one portion movable with said rst mentioned diaphragm and a second portion attached to `said valve casing in a manner to seal oi the refrigerant in said diaphragm chamber from atmosphere, and a biasing spring for said rst men- :tionedl diaphragmfsaid biasing spring being located exteriorly of said seal-oir diaphragm means.

' `31L`An eiparision valve for refrigeration systemsfcom'prising a valve casing, valve means in said casing for controlling the flow of refrigerant from said valve casing, and a diaphragm assembly for actuating said valve means also located in 

